Technical Abstract:
To determine the bioavailability of lutein and b-carotene from kale Brassica oleracea L., a LC-MS method was employed. Extracts of kale grown under an enriched atmosphere of 13CO2 and plasma extracts from human subjects that ingested the 13C-labeled kale were subjected to LC-MS. HPLC separations of plasma and kale extracts were carried out under reverse phase conditions using a C18 column. Gradient elution was used for simultaneous separation of xanthophylls and carotenoids, namely lutein and b- carotene. The HPLC effluent was nebulized using helium and the solvent was removed under vacuum within the dual stage particle- beam interface. In the negative chemicals ionization mode, methane was used as the reagent gas to afford xanthophyll and carotenoid ions that were detected using SIM. Quantification was based on the isotopic abundance ratios of uniformly labeled b- carotene (m/z 576) to the internal standard 2H8-b-carotene (m/z 544) and the ratio of uniformly labeled lutein (m/z 608) to the internal standard, b-apo-8'-carotenal (m/z 416). This study constitutes a major initiative investigating bioavailability of nutrients from foods using the unique resources of several collaborating facilities within BARC.